Critically ill patients, especially those with sepsis and inflammation, often present with altered fluid balance and require fluid resuscitation in the intensive care unit. There is emerging evidence that measures of hydration determined with bioelectrical impedance analysis (BIA) have prognostic value in these patients.

Researchers in Brazil retrospectively assessed the relationship between BIA variables in critically ill children and both the presentation of these patients and the course of their illnesses. They reviewed 7 years of data for 332 children who were on mechanical ventilation, were receiving fluid resuscitation, and for whom BIA had been performed within the first 48 h of admission and at other times during hospitalization. BIA was done using a portable plethysmograph (BIA 101 Quantum II, RJL Systems). Values of resistance (R) and reactance (Xc) were normalized to height (H).

At admission, 152 cases had edema, 212 had septic shock, and 71 had multiple organ dysfunction syndrome (MODS) affecting four or more organ systems. When patients were grouped according to MODS (<4 vs. ≥4) at admission, there was no overlap between the 95% confidence ellipses for the bioimpedance vectors, indicating that this analysis can predict the severity of the patients’ conditions. Statistical analysis showed that low values of both Xc/H and R/H associated with MODS ≥4 (corrected for sex, age, and presence of edema and comorbidities).

For the 211 cases that underwent BIA at discharge, a clear difference was seen in the positions of their bioimpedance vectors between admission and discharge, reflecting an increase in both R/H and Xc/H as their conditions improved. For the 23 patients who died in hospital, there was a trend of worsening (lowering) of R/H or Xc/H.

The authors argued that their study adds “add important evidence to the role of Xc/H and R/H in the monitoring of the critically ill pediatric patients.” They concluded that the “assessment of bioelectrical impedance parameters can be considered a useful tool in monitoring severity of the critically ill pediatric patients. Lower values of R/H and Xc/H could alert the physician to a higher severity.” However, they note that additional studies are needed to assess the roles of R/H and Xc/H as prognostic biomarkers of septic shock and organ dysfunction.